(1) Field of the Invention
The present invention relates to the establishment of multi-path fluid tight pivotal connections and particularly to the delivery of hydraulic fluid under pressure to a movable tool More specifically, the present invention is directed to pivotal fluid couplings which are assembled from modular elements and especially to combinations of such couplings which define an articulated multiple path fluid transmission system. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for employment in a harsh operating environment, such as in proximity to a blast furnace, for the delivery of pressurized hydraulic fluid to a tool such as a tap hole drill. Accordingly, the discussion below will emphasize the operational problems incident to feeding a drill for the tap holes of blast furnaces with hydraulic and/or pneumatic fluid. Such tap hole drilling devices are disclosed and described in U.S. Pat. Nos. 4,097,033, 4,195,825, and 4,201,373. In the case of a tap hole drill the tool is designed to slide along a support bar and the operating fluid for the tool is available at a supply station which is fixed in position relative to the support bar. A plurality of fluid-tight connections must be established between the supply station and the tool which, as may be seen from the above-referenced patents, must be capable of undergoing complex motion.
The drills generally used for opening the tap holes of a shaft furnace, particularly a blast furnace, are percussion devices which, in the prior art, have almost exclusively been pneumatically actuated. The use of pneumatic tools has been dictated by difficulties, which will be discussed below, in reliably delivering hydraulic fluid to the movable drill. A percussion drill requires at least two feed circuits, one for producing rotation of the tool and the other for causing reciprocation of the bit thereof. If the drill is capable of performing supplementary actions, for example, rotation in two opposite directions and/or delivering is percussive output in two directions, the number of required fluidic feed circuits will be correspondingly increased. Furthermore, tap hole drills are customarily equipped with a blower which serves for the removal of cuttings produced during operation while simultaneously cooling the drill bit and its crown. The blower requires a separate compressed air feed conduit. Thus, it may be seen that a multi-path fluid delivery system with articulated couplings is required between the above-mentioned fixed predetermined supply station, where the pneumatic or hydraulic fluid is available, and the drill itself. The delivery system must accomodate movement of the drill along the support bar over a distance of several meters.
The delivery system which has found the most widespread usage in the prior art comprises simply the employment of flexible hoses between the operating fluid source (supply station) and the tool. This approach to solving the problem of delivering the operating fluid to a movable tap hole drill has numerous disadvantages. Firstly, a complicated and expensive tensioning and winding apparatus is required and the various suspended hoses and cables in the vicinity of the drill pose a safety hazard to the operator. Additionally, the hoses hang over the tap spout during the drilling operation and are thus liable to be damaged by molten metal splashed thereon when the tap hole is opened. In the case of a hydraulic feed, this presents the additional safety hazard of the possibility of fire resulting from the leakage of the hydraulic fluid.
One approach to solving the above-discussed problems incident to the use of flexible hoses is disclosed in above-mentioned U.S. Pat. No. 4,097,033. This approach contemplates the use of rigid conduits interconnected by means of rotary couplings to provide for the feed of the operating fluid to the drill. In order for the feed system of U.S. Pat. No. 4,097,033 to function correctly, however, the rotation axes of the rotary couplings must remain precisely parallel at all times. Any deviation from such parallelism will cause binding, whereupon the drill cannot be moved, and/or will cause rapid deterioration of the couplings with the resultant leakage of operating fluid. Because of manufacturing tolerances, it is exceedingly difficult, if not impossible, to achieve and maintain the requisite parallelism, particularly in the harsh operating condition of a blast furnace where thermally induced deformation of components will occur.
The above-discussed problems may be overcome with comparative ease in those cases where the drill is exclusively a pneumatic device. Thus, by way of example, in the case of a pneumatic drill the compressed air may be supplied to the drill via a suitable main conduit, constructed in the manner disclosed in U.S. Pat. No. 4,097,033, and the stream of compressed air may be subdivided within the drill itself, by means of remotely controlled valves, into as many separate streams as there are functions to be performed. This, of course, requires the inclusion in the drill of valves, which are themselves operated by compressed air, and auxiliary conduits must be provided for valve control purposes. These control fluid supply conduits, however, are of very small cross section and are more or less flexible and thus do not present the above-discussed problems. Furthermore, since all of the pressures employed in a pneumatic system are moderate, and most importantly because it is not necessary to provide for return of the operating pneumatic fluid to the source, any problems encountered may be easily solved through the use of compressible seals and other known means. Thus, in an entirely pneumatic system, it is necessary to employ only a single main conduit and, in part since the pneumatic pressures never exceed 5-8 bar, it is possible to overcome the problems of maintaining parallelism between the articulation axes by providing a rotating and oscillating coupling and a pair of Cardan-type connections with bellows-type compensators. Under these circumstances, even if some minor leakage were to occur, it would not have any serious detrimental effect.
The above-briefly discussed techniques for delivering pneumatic operating fluid to a tap hole drill are, unfortunately, not applicable to hydraulic systems. Whereas a pneumatic drill will typically operate with a pressure in the range of 5-8 bar, as discussed above, the pressure of the hydraulic fluid employed for operating a tap hole drill will typically be in the range of 100 to 200 bar. Further, a single main feed conduit is inadequate in a hydraulic system since the hydraulic fluid must be returned to a resevoir rather than merely being exhausted to the ambient atmosphere at the drill. If a reliable hydraulic supply could be established for a tap hole drill, however, significant operating advantages would be realized. By way of example, a hydraulic tool produces substantially less noise during operation when compared to a similar pneumatic tool. Also, the quantities of compressed gas required to operate a pneumatic drill are comparatively large while the hydraulic drill, partly because of its higher operating pressure, consumes considerably less fluid and requires much less energy for operation. In fact, the energy consumption of a hydraulic motor is about 50% below that of a comparable pneumatic motor. It is additionally to be noted that a tap hole drill will be operated in tandem with a clay gun which is employed to plug the tap hole. Since the clay gun is hydraulically operated, a source of pressurized hydraulic fluid is available. It would thus be advantageous to employ the hydraulic supply of the clay gun for operating the drill. Unfortunately, there has not previously been a reliable manner for simultaneously establishing a plurality of flow paths for hydraulic fluid from a stationary source to a load, such as a tap hole drill, which undergoes complex movements.